Reference Signal Configuration for Extension Carriers And Carrier Segments

ABSTRACT

Reference signals configured for use with extension carriers and/or carrier segments are described. Reference signals for extension carriers and/or carrier segments may include demodulation reference signals (e.g., user equipment-specific reference signals), cell-specific reference signals, and channel-state information reference signals. Methods, systems and apparatuses for configuring extension carriers and/or carrier segments with one or more of the reference signals (e.g., positioning one or more reference signal symbols in extension carriers and/or carrier segments) are described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional patent applicationNo. 61/523,276, filed Aug. 12, 2011, which is incorporated herein byreference in its entirety.

BACKGROUND

A wireless communication network, for example a wireless networkconfigured in accordance with Third Generation Partnership Project(3GPP) standards, may support transmission of signals (e.g., voiceand/or data signals) over a carrier (e.g., a primary carrier) that maybe established between one or more components of a core network (CN) ofthe wireless communications network and user equipment (UE) associatedwith the wireless communications network. One or both of the CN and theUE may transmit reference signals over the carrier that may be used, forexample, to perform channel estimation of the carrier.

A respective portion of wireless communication network bandwidth thatmay be made available for use by a UE may be expanded, for example byemploying one or more carrier expansion techniques. Carrier expansiontechniques may include employing one or more extension carriersconfigured to supplement the primary carrier. Signaling schemes that maybe employed for a primary carrier, for example positions of referencesignals within the primary carrier, may not provide optimal performanceif employed for an extension carrier.

SUMMARY

As described herein, reference signals may be positioned in variouslocations within respective resource elements of an extension carrierand/or a carrier segment, for instance such that transmissionperformance between a CN and a UE over the extension carrier and/orcarrier segment may be optimized.

A method may include transmitting a first timeslot of a subcarrier. Thefirst timeslot may have a first plurality of resource elements that maybe ordered from a first resource element to a last resource element.Transmitting the first timeslot may include transmitting a first symbolin a select one of the first plurality of resource elements that may notbe the last resource element. The first symbol may be a userequipment-specific demodulation reference signal. Transmitting the firsttimeslot may include transmitting a second symbol in the last resourceelement of the first plurality of resource elements. The second symbolmay be other than a user equipment-specific demodulation referencesignal.

A wireless transmit/receive unit (WTRU) may include a processor that maycause the WTRU to transmit a first timeslot of a subcarrier. The firsttimeslot may have a first plurality of resource elements that areordered from a first resource element to a last resource element. TheWTRU may transmit the first timeslot by transmitting a first symbol in aselect one of the first plurality of resource elements that may not bethe last resource element. The first symbol may be a userequipment-specific demodulation reference signal. The WTRU may transmitthe first timeslot by transmitting a second symbol in the last resourceelement of the first plurality of resource elements. The second symbolmay be other than a user equipment-specific demodulation referencesignal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A depicts a system diagram of an example communications system inwhich one or more disclosed embodiments may be implemented.

FIG. 1B depicts a system diagram of an example wireless transmit/receiveunit (WTRU) that may be used within the communications systemillustrated in FIG. 1A.

FIG. 1C depicts a system diagram of an example radio access network andan example core network that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 1D depicts a system diagram of an example radio access network andan example core network that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 1E depicts a system diagram of an example radio access network andan example core network that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 2 is a block diagram of an example resource block grid structurethat may comprise a respective portion of an extension carrier.

FIG. 3 is a block diagram of an example carrier segment structure.

FIG. 4 includes block diagrams depicting positions for demodulationreference signals (DM-RS) for two antenna ports, in accordance with 3GPPRelease 10.

FIG. 5 includes block diagrams depicting DM-RS positions for extensioncarriers and/or carrier segments for two antenna ports in accordancewith an embodiment.

FIG. 6 includes block diagrams depicting DM-RS positions for extensioncarriers and/or carrier segments for two antenna ports in accordancewith an embodiment.

FIG. 7 includes block diagrams depicting DM-RS positions for extensioncarriers and/or carrier segments for two antenna ports in accordancewith an embodiment.

FIG. 8 includes block diagrams depicting DM-RS positions for extensioncarriers and/or carrier segments for two antenna ports in accordancewith an embodiment.

FIGS. 9A and 9B include block diagrams depicting DM-RS positions forextension carriers and/or carrier segments for four antenna ports inaccordance with an embodiment.

FIG. 10 is a block diagram depicting DM-RS positions for an extensioncarrier and/or carrier segment for an antenna port in accordance with anembodiment.

FIG. 11 is a block diagram depicting Cell-specific Reference Signal(CRS) positions for an extension carrier and/or carrier segment for anantenna port in accordance with an embodiment.

FIG. 12 is a block diagram depicting Cell-specific Reference Signal(CRS) positions for an extension carrier and/or carrier segment for anantenna port in accordance with an embodiment.

FIG. 13 is a block diagram depicting Cell-specific Reference Signal(CRS) positions for an extension carrier and/or carrier segment for anantenna port in accordance with an embodiment.

DETAILED DESCRIPTION

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. For example, awireless network (e.g., a wireless network comprising one or morecomponents of the communications system 100) may be configured such thatbearers that extend beyond the wireless network (e.g., beyond a walledgarden associated with the wireless network) may be assigned QoScharacteristics.

The communications system 100 may be a multiple access system thatprovides content, such as voice, data, video, messaging, broadcast,etc., to multiple wireless users. The communications system 100 mayenable multiple wireless users to access such content through thesharing of system resources, including wireless bandwidth. For example,the communications systems 100 may employ one or more channel accessmethods, such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include at leastone wireless transmit/receive unit (WTRU), such as a plurality of WTRUs,for instance WTRUs 102 a, 102 b, 102 c, and 102 d, a radio accessnetwork (RAN) 104, a core network 106, a public switched telephonenetwork (PSTN) 108, the Internet 110, and other networks 112, though itshould be appreciated that the disclosed embodiments contemplate anynumber of WTRUs, base stations, networks, and/or network elements. Eachof the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d may be configuredto transmit and/or receive wireless signals and may include userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106, the Internet 110,and/or the networks 112. By way of example, the base stations 114 a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B, a HomeNode B, a Home eNode B, a site controller, an access point (AP), awireless router, and the like. While the base stations 114 a, 114 b areeach depicted as a single element, it should be appreciated that thebase stations 114 a, 114 b may include any number of interconnected basestations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals within aparticular geographic region, which may be referred to as a cell (notshown). The cell may further be divided into cell sectors. For example,the cell associated with the base station 114 a may be divided intothree sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, infrared (IR), ultraviolet (UV), visible light, etc.). Theair interface 116 may be established using any suitable radio accesstechnology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed DownlinkPacket Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106.

The RAN 104 may be in communication with the core network 106, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. For example, the core network 106may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it should be appreciatedthat the RAN 104 and/or the core network 106 may be in direct orindirect communication with other RANs that employ the same RAT as theRAN 104 or a different RAT. For example, in addition to being connectedto the RAN 104, which may be utilizing an E-UTRA radio technology, thecore network 106 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106 may also serve as a gateway for the WTRUs 102 a,102 b, 102 c, 102 d to access the PSTN 108, the Internet 110, and/orother networks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) andthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired or wireless communications networks ownedand/or operated by other service providers. For example, the networks112 may include another core network connected to one or more RANs,which may employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 130, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It should be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it should be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In another embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and receive both RF and light signals. It should be appreciatedthat the transmit/receive element 122 may be configured to transmitand/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It should be appreciated that the WTRU 102may acquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of an embodiment of the communicationssystem 100 that includes a RAN 104 a and a core network 106 a thatcomprise example implementations of the RAN 104 and the core network106, respectively. As noted above, the RAN 104, for instance the RAN 104a, may employ a UTRA radio technology to communicate with the WTRUs 102a, 102 b, and 102 c over the air interface 116. The RAN 104 a may alsobe in communication with the core network 106 a. As shown in FIG. 1C,the RAN 104 a may include Node-Bs 140 a, 140 b, 140 c, which may eachinclude one or more transceivers for communicating with the WTRUs 102 a,102 b, 102 c over the air interface 116. The Node-Bs 140 a, 140 b, 140 cmay each be associated with a particular cell (not shown) within the RAN104 a. The RAN 104 a may also include RNCs 142 a, 142 b. It should beappreciated that the RAN 104 a may include any number of Node-Bs andRNCs while remaining consistent with an embodiment.

As shown in FIG. 1C, the Node-Bs 140 a, 140 b may be in communicationwith the RNC 142 a. Additionally, the Node-B 140 c may be incommunication with the RNC 142 b. The Node-Bs 140 a, 140 b, 140 c maycommunicate with the respective RNCs 142 a, 142 b via an Iub interface.The RNCs 142 a, 142 b may be in communication with one another via anIur interface. Each of the RNCs 142 a, 142 b may be configured tocontrol the respective Node-Bs 140 a, 140 b, 140 c to which it isconnected. In addition, each of the RNCs 142 a, 142 b may be configuredto carry out or support other functionality, such as outer loop powercontrol, load control, admission control, packet scheduling, handovercontrol, macrodiversity, security functions, data encryption, and thelike.

The core network 106 a shown in FIG. 1C may include a media gateway(MGW) 144, a mobile switching center (MSC) 146, a serving GPRS supportnode (SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. Whileeach of the foregoing elements is depicted as part of the core network106 a, it should be appreciated that any one of these elements may beowned and/or operated by an entity other than the core network operator.

The RNC 142 a in the RAN 104 a may be connected to the MSC 146 in thecore network 106 a via an IuCS interface. The MSC 146 may be connectedto the MGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102 a,102 b, 102 c with access to circuit-switched networks, such as the PSTN108, to facilitate communications between the WTRUs 102 a, 102 b, 102 cand traditional land-line communications devices.

The RNC 142 a in the RAN 104 a may also be connected to the SGSN 148 inthe core network 106 a via an IuPS interface. The SGSN 148 may beconnected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between and the WTRUs102 a, 102 b, 102 c and IP-enabled devices.

As noted above, the core network 106 a may also be connected to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1D is a system diagram of an embodiment of the communicationssystem 100 that includes a RAN 104 b and a core network 106 b thatcomprise example implementations of the RAN 104 and the core network106, respectively. As noted above, the RAN 104, for instance the RAN 104b, may employ an E-UTRA radio technology to communicate with the WTRUs102 a, 102 b, and 102 c over the air interface 116. The RAN 104 b mayalso be in communication with the core network 106 b.

The RAN 104 b may include eNode-Bs 140 d, 140 e, 140 f, though it shouldbe appreciated that the RAN 104 b may include any number of eNode-Bswhile remaining consistent with an embodiment. The eNode-Bs 140 d, 140e, 140 f may each include one or more transceivers for communicatingwith the WTRUs 102 a, 102 b, 102 c over the air interface 116. In oneembodiment, the eNode-Bs 140 d, 140 e, 140 f may implement MIMOtechnology. Thus, the eNode-B 140 d, for example, may use multipleantennas to transmit wireless signals to, and receive wireless signalsfrom, the WTRU 102 a.

Each of the eNode-Bs 140 d, 140 e, and 140 f may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 1D, theeNode-Bs 140 d, 140 e, 140 f may communicate with one another over an X2interface.

The core network 106 b shown in FIG. 1D may include a mobilitymanagement gateway (MME) 143, a serving gateway 145, and a packet datanetwork (PDN) gateway 147. While each of the foregoing elements isdepicted as part of the core network 106 b, it should be appreciatedthat any one of these elements may be owned and/or operated by an entityother than the core network operator.

The MME 143 may be connected to each of the eNode-Bs 140 d, 140 e, and140 f in the RAN 104 b via an Si interface and may serve as a controlnode. For example, the MME 143 may be responsible for authenticatingusers of the WTRUs 102 a, 102 b, 102 c, bearer activation/deactivation,selecting a particular serving gateway during an initial attach of theWTRUs 102 a, 102 b, 102 c, and the like. The MME 143 may also provide acontrol plane function for switching between the RAN 104 b and otherRANs (not shown) that employ other radio technologies, such as GSM orWCDMA.

The serving gateway 145 may be connected to each of the eNode Bs 140 d,140 e, 140 f in the RAN 104 b via the Si interface. The serving gateway145 may generally route and forward user data packets to/from the WTRUs102 a, 102 b, 102 c. The serving gateway 145 may also perform otherfunctions, such as anchoring user planes during inter-eNode B handovers,triggering paging when downlink data is available for the WTRUs 102 a,102 b, 102 c, managing and storing contexts of the WTRUs 102 a, 102 b,102 c, and the like.

The serving gateway 145 may also be connected to the PDN gateway 147,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 106 b may facilitate communications with othernetworks. For example, the core network 106 b may provide the WTRUs 102a, 102 b, 102 c with access to circuit-switched networks, such as thePSTN 108, to facilitate communications between the WTRUs 102 a, 102 b,102 c and traditional land-line communications devices. For example, thecore network 106 b may include, or may communicate with, an IP gateway(e.g., an IP multimedia subsystem (IMS) server) that serves as aninterface between the core network 106 b and the PSTN 108. In addition,the core network 106 b may provide the WTRUs 102 a, 102 b, 102 c withaccess to the networks 112, which may include other wired or wirelessnetworks that are owned and/or operated by other service providers.

FIG. 1E is a system diagram of an embodiment of the communicationssystem 100 that includes a RAN 104 c and a core network 106 c thatcomprise example implementations of the RAN 104 and the core network106, respectively. The RAN 104, for instance the RAN 104 c, may be anaccess service network (ASN) that employs IEEE 802.16 radio technologyto communicate with the WTRUs 102 a, 102 b, and 102 c over the airinterface 116. As described herein, the communication links between thedifferent functional entities of the WTRUs 102 a, 102 b, 102 c, the RAN104 c, and the core network 106 c may be defined as reference points.

As shown in FIG. 1E, the RAN 104 c may include base stations 102 a, 102b, 102 c, and an ASN gateway 141, though it should be appreciated thatthe RAN 104 c may include any number of base stations and ASN gatewayswhile remaining consistent with an embodiment. The base stations 102 a,102 b, 102 c may each be associated with a particular cell (not shown)in the RAN 104 c and may each include one or more transceivers forcommunicating with the WTRUs 102 a, 102 b, 102 c over the air interface116. In one embodiment, the base stations 140 g, 140 h, 140 i mayimplement MIMO technology. Thus, the base station 140 g, for example,may use multiple antennas to transmit wireless signals to, and receivewireless signals from, the WTRU 102 a. The base stations 140 g, 140 h,140 i may also provide mobility management functions, such as handofftriggering, tunnel establishment, radio resource management, trafficclassification, quality of service (QoS) policy enforcement, and thelike. The ASN Gateway 141 may serve as a traffic aggregation point andmay be responsible for paging, caching of subscriber profiles, routingto the core network 106 c, and the like.

The air interface 116 between the WTRUs 102 a, 102 b, 102 c and the RAN104 c may be defined as an R1 reference point that implements the IEEE802.16 specification. In addition, each of the WTRUs 102 a, 102 b, and102 c may establish a logical interface (not shown) with the corenetwork 106 c. The logical interface between the WTRUs 102 a, 102 b, 102c and the core network 106 c may be defined as an R2 reference point,which may be used for authentication, authorization, IP hostconfiguration management, and/or mobility management.

The communication link between each of the base stations 140 g, 140 h,140 i may be defined as an R8 reference point that includes protocolsfor facilitating WTRU handovers and the transfer of data between basestations. The communication link between the base stations 140 g, 140 h,140 i and the ASN gateway 141 may be defined as an R6 reference point.The R6 reference point may include protocols for facilitating mobilitymanagement based on mobility events associated with each of the WTRUs102 a, 102 b, 102 c.

As shown in FIG. 1E, the RAN 104 c may be connected to the core network106 c. The communication link between the RAN 104 c and the core network106 c may defined as an R3 reference point that includes protocols forfacilitating data transfer and mobility management capabilities, forexample. The core network 106 c may include a mobile IP home agent(MIP-HA) 144, an authentication, authorization, accounting (AAA) server156, and a gateway 158. While each of the foregoing elements is depictedas part of the core network 106 c, it should be appreciated that any oneof these elements may be owned and/or operated by an entity other thanthe core network operator.

The MIP-HA may be responsible for IP address management, and may enablethe WTRUs 102 a, 102 b, and 102 c to roam between different ASNs and/ordifferent core networks. The MIP-HA 154 may provide the WTRUs 102 a, 102b, 102 c with access to packet-switched networks, such as the Internet110, to facilitate communications between the WTRUs 102 a, 102 b, 102 cand IP-enabled devices. The AAA server 156 may be responsible for userauthentication and for supporting user services. The gateway 158 mayfacilitate interworking with other networks. For example, the gateway158 may provide the WTRUs 102 a, 102 b, 102 c with access tocircuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionallandline communications devices. In addition, the gateway 158 mayprovide the WTRUs 102 a, 102 b, 102 c with access to the networks 112,which may include other wired or wireless networks that are owned and/oroperated by other service providers.

Although not shown in FIG. 1E, it should be appreciated that the RAN 104c may be connected to other ASNs and the core network 106 c may beconnected to other core networks. The communication link between the RAN104 c the other ASNs may be defined as an R4 reference point, which mayinclude protocols for coordinating the mobility of the WTRUs 102 a, 102b, 102 c between the RAN 104 c and the other ASNs. The communicationlink between the core network 106 c and the other core networks may bedefined as an R5 reference point, which may include protocols forfacilitating interworking between home core networks and visited corenetworks.

A WTRU operating within a single serving cell of an LTE system (e.g., inaccordance with 3GPP Releases 8, 9, 10 and/or future releases(hereinafter “R8+”)) may support transmission rates up to 100 Mbps fortransmissions on a downlink (DL), and up to 50 Mbps for transmissions onan uplink (UL) for a 2×2 (e.g., dual-antenna MIMO) configuration. The DLtransmission scheme of an LTE system may be based on an OFDMA airinterface. In accordance with R8+, an LTE system may support scalabletransmission bandwidth. For example, transmission bandwidth may scale upand/or down using any of a defined set of bandwidths, for instance 1.4MHz, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz or 20 MHz within which roughly 6,15, 25, 50, 75, 100 resource blocks, respectively, may be transmitted.

In R8+LTE systems, (e.g., systems in accordance with 3GPP Releases 10and/or future releases (hereinafter “R10+”) that may support carrieraggregation), each radio frame may have a duration of approximately 10milliseconds (ms), and may be formed from ten substantiallyequally-sized sub-frames, such subframe SF1 depicted in FIG. 2. Eachsubframe may have a duration of approximately 1 ms. Each sub-frame maybe formed from two substantially equally-sized timeslots, such as TS1and TS2 of SF1. Each timeslot may have a duration of approximately 0.5ms. Each timeslot may comprise (and may be decomposed into) a respectivenumber of symbols, for example seven OFDM symbols in accordance with aregular cyclic prefix (CP) length, six OFDM symbols in accordance withan extended cyclic prefix (CP) length, or the like.

Each subframe may comprise a first resource block (RB) and a second RB,such as RB1 and RB2, respectively, that may define a resource blockpair. Each resource block of each pair may be associated with aparticular timeslot of each subframe. Each subframe, may comprise (andmay be decomposed into) twelve subcarriers, such as subcarriersSC1-SC12. The twelfth subcarrier (SC12) may be referred to as the lastsubcarrier of the subframe. The subcarriers may be configured inaccordance with predefined subcarrier spacing. For instance, inaccordance with R8 and R9 LTE systems, the subcarrier spacing may be 15kHz. In an alternative, reduced sub-carrier spacing mode, thesub-carrier spacing may be 7.5 kHz.

Each subcarrier may comprise (and may be decomposed into) a plurality ofresource elements. Each resource element (RE) may correspond to a selectsub-carrier during a select OFDM symbol interval. Twelve consecutivesubcarriers during a timeslot may form one RB. In accordance with anexample of normal CP length, each RB, such as each of RB1 and RB2, maycomprise 84 REs, (12 subcarriers×7 OFDM symbols). Accordingly, eachsubcarrier may include a plurality of REs in accordance with the CPlength employed, for instance SC1-SC12 each comprising RE1-RE7associated with RB1 and RE1-RE7 associated with RB2.

In each timeslot of each subcarrier, respectively, each RE 1 may bereferred to as a first resource element of the timeslot, each RE2 may bereferred to as a second resource element of the timeslot, each RE3 maybe referred to as a third resource element of the timeslot, each RE4 maybe referred to as a fourth resource element of the timeslot, each RE5may be referred to as the third resource element of the timeslot, eachRE6 may be referred to as the sixth resource element of the timeslot,and each RE7 may be referred to as one or both of the seventh resourceelement of the timeslot and the last resource element of the timeslot.In this regard, each timeslot may comprise a respective plurality ofresource elements (e.g., RE1-RE7) that are ordered from a first resourceelement (e.g., RE1) to a last resource element (e.g., RE7). If extendedCP is employed, each timeslot may only contain six REs, and each RE6 maytherefore be referred to as one or both of the sixth resource element ofthe timeslot and the last resource element of the timeslot.

A carrier (e.g., a DL carrier) may include a scalable number of resourceblocks, for instance from 6 RBs to 110 RBs. The number of RBs may bescaled up and/or down in accordance with overall scalable transmissionbandwidth, for instance in accordance with any herein describedpre-defined bandwidth.

A basic time-domain unit for dynamic scheduling may be one subframe(e.g., two consecutive timeslots), and may be referred to as a resourceblock pair.

Select subcarriers on some OFDM symbols may be allocated to carry pilotsignals in the time-frequency grid. A select number of subcarriers atedges of the transmission bandwidth may not be transmitted, for example,to comply with spectral mask requirements.

A number of multi-antenna transmission modes may be supported. In LTEsystems, each multi-antenna transmission modes may be referred to as aselect transmission mode (TM). The TMs may differ relative to eachother, for example in input-to-antenna-port mapping and/or in whatreference signals may be used for demodulation. Transmission modesdefined for Downlink Shared Channel (DL-SCH) transmissions may include:TM1 (single-antenna transmission); TM2 (transmit diversity); TM3(open-loop codebook-based precoding if more than one layer, elsetransmit diversity if rank-one transmission); TM4 (closed-loopcodebook-based precoding); TM5 (multi-user-MIMO version of TM4); TM6(codebook-based precoding limited to single layer transmission); TM7 (R8non-codebook-based precoding with single layer transmission); TM8 (R9non-codebook-based precoding supporting up to two layers;) and TM9 (R10non-codebook-based precoding supporting up to eight layers).

In R8+LTE systems, a UE may receive one or more reference signals (RS)on the DL. Reference signals may include cell-specific reference signals(CRS), demodulation reference signals (DM-RS) that may be UE-specific,and/or channel state information (CSI) RS (CSI-RS).

A UE may use a CRS for channel estimation for coherent demodulation ofany DL physical channel. An exception may include a Physical Multicastdata Channel (PMCH) and/or a Physical Data Shared Channel (PDSCH), whichmay be configured with TM7, TM8 or TM9. A UE may use a CRS for channelstate information (CSI) measurements. A UE may use a CRS forcell-selection and/or mobility-related measurements. A CRS may bereceived in any subframe. There may be one CRS for each antenna ports(e.g., 1, 2, or 4). A CRS may occupy at least the first andthird-to-last OFDM symbol of each time slot.

A DM-RS may be specific to a select UE. A UE may use a DM-RS for channelestimation, for example for demodulation of a PDSCH configured with TM7,TM8 or TM9. A DM-RS may be transmitted in resource blocks assigned tothe PDSCH transmission for a select UE.

A UE may use a CSI-RS for CSI measurements. CSI-RSs may only be used forTM9, and may be less densely transmitted by a network than CRSs.

A UE may be configured with one or more carrier segments for a givenserving cell. If carrier aggregation is configured, the serving cell maybe any of a Primary Cell (PCell) and a Serving Cell (SCell) of the UE'sconfiguration. Each carrier segment may define a set of physical RBsavailable to the UE that may not be members of an addressable set of RBssupported for the given serving cell. Each of the carrier segments maybe appended to the supported set of RBs (supported-RB set) and/or toother carrier segments. Carrier segments may be appended in a number ofways. For example, carrier segments may be appended so as to form acontiguous bandwidth extension to the supported-RB set (and/or to othercarrier segments appended to the supported-RB set and/or other carriersegments).

Referring to FIG. 3, a block diagram illustrating an example DL RB-gridstructure for a WTRU configured with a plurality of carrier segments isshown. This DL RB-grid structure may define an addressable superset ofRBs that includes the supported-RB set and two carrier segments appendedas contiguous bandwidth extensions to the supported-RB set. Theillustrated DL RB-grid structure (hereinafter “extended-RB-supersetstructure”) may be part of, integrated into and/or associated with a UEphysical resource map on which transmissions (uplink or downlink) may bescheduled by the network.

As shown in FIG. 3, the extended-RB-superset structure may have acarrier bandwidth, B. The bandwidth B may be an aggregation of carrierbandwidths B₀, B_(D) and B_(U) of the supported-RB set, carrier SEGMENT1 and carrier SEGMENT 2, respectively. The supported-RB bandwidth B₀ maybe a bandwidth supported for the given serving cell, and may be definedby a standard to which the associated serving cell conforms. Whenconfigured to operate on the associated serving cell, the UE mayinitially operate using the supported-RB bandwidth B₀. The UE may besubsequently configured to operate using one or both of thecarrier-segment bandwidths B_(D), B_(U) in addition to (or at leastpartially, in lieu of) supported-RB bandwidth B₀.

A UE may be configured with one or more serving cells on which itoperates according to one or more extension carriers; each of which maybe a frequency on which the UE may operate. The serving cells mayinclude a SCell of the UE's multicarrier configuration. The SCell may beconfigured with uplink resources (e.g., SCell DL and SCell UL), withoutuplink resources (e.g., SCell DL only) and/or only uplink resources(e.g., SCell UL only). The SCell may be configured with SCell UL only,when, for example, the SCell UL is in substantially the same band as thePCell of the UE's configuration.

The UE may perform one or more of the following for a SCell configuredas an extension carrier. The may receive downlink transmissions, such asSCell DL (e.g., on PDSCH). The UE may perform uplink transmissions, suchas SCell UL (e.g., on PUSCH). The UE may receive reference signals(e.g., one or more cell-specific CRSs, one or more UE-specific DM-RSs,and/or one or more CSI-RSs). The UE may transmit Sounding and ReferenceSignals (SRS) signals.

The UE may not perform one or more of the following for a serving cellconfigured as an extension carrier. The UE may receive primarysynchronization signals (PSS) and/or secondary synchronization signals(SSS). The UE may receive broadcasted System Information (SI) (e.g., ona broadcast channel (BCCH) if present). The UE may receive and/or decodedownlink control signaling on physical control channels of theassociated serving cell (e.g., a Physical Data Control Channel (PDCCH)and/or a Physical Hybrid ARQ Indicator Channel (PHICH) and/or a PhysicalControl Format Indicator Channel (PCFICH) if present).

A component carrier (CC) may include a frequency on which a UE operates.A UE may receive one or more transmissions on a downlink CC (DL CC). ADL CC may include at least one DL physical channel, such as a pluralityof DL physical channels. For an LTE system, downlink physical channelsmay include a Physical Control Format Indicator Channel (PCFICH), aPhysical Hybrid ARQ Indicator Channel (PHICH), a Physical Data ControlChannel (PDCCH), a Physical Multicast data Channel (PMCH) and/or aPhysical Data Shared Channel (PDSCH). On the PCFICH, the UE may receivecontrol data (e.g., indicating the size of a control region of the DLCC). On the PHICH, a UE may receive control data (e.g., indicating HARQAcknowledgement/Negative Acknowledgement (HARQ A/N, HARQ ACK/NACK, orHARQ-ACK) feedback for a previous uplink transmission. On a PDCCH, a UEmay receive downlink control information (DCI) messages, which may beused for scheduling of downlink and/or uplink resources. On a PDSCH, aUE may receive user and/or control data.

A UE may perform one or more transmissions on an uplink CC (UL CC). AnUL CC may include at least one UL physical channel, such as a pluralityof UL physical channels. A UE may transmit on an uplink CC (UL CC). Foran LTE system, uplink physical channels may include a Physical UplinkControl Channel (PUCCH) and/or a Physical Uplink Shared Channel (PUSCH).On a PUSCH, a UE may transmit user and/or control data. On a PUCCH, andin some cases on a PUSCH, the UE may transmit uplink control information(e.g., CQI/PMI/RI or SR) and/or hybrid automatic repeat request (HARQ)acknowledgement/negative acknowledgement (ACK/NACK) feedback. On a ULCC, the UE may be allocated dedicated resources for transmission ofSounding and Reference Signals (SRS).

A cell may comprise a DL CC that may be linked to a UL CC, for instancebased on the system information (SI) received by the UE broadcasted onthe DL CC and/or using dedicated configuration signaling from thenetwork. For example, when broadcasted on the DL CC, the UE may receivethe uplink frequency and bandwidth of the linked UL CC as part of thesystem information element (e.g., when in RRC_IDLE for LTE, or when inidle/CELL_FACH for WCDMA (when the WTRU does not yet have a radioresource connection to the network)).

A Primary Cell (PCell) may comprise a cell operating on a primaryfrequency in which the UE performed initial access to the system (e.g.,in which the UE performed an initial connection establishment procedureor initiated a connection re-establishment procedure), a cell indicatedas a primary cell in a handover procedure, or the like. A PCell maycorrespond to a frequency indicated as part of a radio resourceconnection configuration procedure. Some functions may be only supportedon a PCell. For example, the UL CC of a PCell may correspond to a CCwhose physical uplink control channel resources may be configured tocarry HARQ ACK/NACK feedback for a given UE.

For example, in LTE systems, a UE may use a PCell to derive parametersfor security functions and/or for upper layer system information such asNAS mobility information. Other functions that may be supported on aPCell DL include system information (SI) acquisition, change monitoringprocedures on a broadcast channel (BCCH), paging, and the like.

A Secondary Cell (SCell) may include a cell operating on a secondaryfrequency that may be configured once a radio resource controlconnection is established and that may be used to provide additionalradio resources. System information relevant for operation in a SCellmay be provided using dedicated signaling (e.g., when a SCell is addedto the UE's configuration). Although associated parameters may havedifferent values than those broadcast on the downlink of a SCell usingthe system information (SI) signaling, this information may be referredto as SI of the concerned SCell, independently of how the UE acquiresthe information.

PCell DL and PCell UL may correspond to the DL CC and the UL CC of thePCell, respectively. SCell DL and SCell UL may correspond to the DL CCand the UL CC (if configured) of a SCell, respectively.

A serving cell may include a primary cell (PCell) or a secondary cell(SCell). For a UE that is not configured with a SCell or that does notsupport operation on multiple component carriers (e.g., does not supportcarrier aggregation), there may be only one serving cell comprising thePCell. For a UE that is configured with at least one SCell, servingcells may include a set of one or more cells comprising the PCell andone or more configured SCells.

When a UE is configured with at least one SCell, there may be one PCellDL and one PCell UL and, for each configured SCell, there may be oneSCell DL and one SCell UL (if configured).

In accordance with a LTE R10 DL, for a given antenna port, DM-RS may betransmitted only on resource blocks that a corresponding PDSCH is mappedto, and may be transmitted only in a predefined set of OFDM symbols in asubframe. For example, as depicted in FIG. 4, using normal CP forantenna ports A and B (which may be any of antenna ports 7, 8 . . .and/or, 14), DM-RSs may be transmitted in the sixth and seventh OFDMsymbol (e.g., RE6 and RE7) in each timeslot in a subframe.

The illustrated locations of OFDM symbols for DM-RS may be used becauseother physical channels and/or signals (e.g., PDCCH and CRS) may bemapped to other OFDM symbols. For example, a PDCCH region may beexpanded to REs in one or more, up to the first three OFDM symbols(e.g., RE1 up to RE3) in at least the first timeslot in a subframe. Assuch, it may not be desirable to locate DM-RS in any of the first threeOFDM symbols in the first timeslot where PDCCH may be transmitted. Inaddition, the CRS for one or more antenna ports (e.g., 0, 1, 2, 3) maybe placed in REs in one or more of the first, second, and/or fourth OFDMsymbols (e.g., RE1, RE2, and RE4) in each timeslot in a subframe. Assuch, the sixth and seventh symbols (e.g., in the first timeslot (TS1))may be desirable locations for DM-RS transmission in a DL.

In accordance with locating DM-RSs in the sixth and seventh OFDMsymbols, channel estimation for the first OFDM symbol through the fifthOFDM symbol in the first timeslot may have to be performed (e.g., usingan extrapolation based on DM-RS in the sixth and seventh OFDM symbols inthe first timeslot). Extrapolation based channel estimation may resultin PDSCH performance degradation. As described herein, DM-RS locationsfor extension carriers and/or carrier segments may be adapted (e.g., toperform channel estimation in extension carriers and/or carrier segmentswithout using extrapolation based channel estimation).

In the absence of synchronization signals (e.g., PSS/SSS) in extensioncarriers, synchronization operation in an associated serving cell maynot be performed properly, unless there is a signal which may be used toassist the synchronization operation. Various CRS for extension carriersand/or carrier segments may be adapted for several purposes, including,for example, synchronization.

In a DL resource grid structure (e.g., in accordance with LTE R10), theRE locations for DM-RSs for respective configured antenna ports (e.g.,RE6 and RE7) may be selected based at least in part upon exclusion of REpositions reserved for the PDCCH region and CRS of a serving cell. Asdescribed herein, one or more extension carriers and/or carrier segmentsmay be configured with various mappings of RE locations to DM-RSs forone or more configured antenna ports for a UE. The RE-to-DM-RS mappingsfor extension carriers and/or carrier segments may be configured in anabsence of LTE R10 restrictions (e.g., selecting RE positions for DM-RSsbased upon PDCCH and/or CRS), for instance because the PDCCH and/or CRSmay not be configured for extension carriers and/or carrier segments. RElocations for DM-RSs may take precedence over the RE positioning for oneor both of the PDCCH and/or CRS.

With continued reference to FIG. 4, DM-RSs may be located in the sixthand seventh OFDM symbols (e.g., RE6 and RE7) in each timeslot (e.g., TS1and TS2) of a subframe, for example, for two antenna ports A and B,respectively, and using normal CP, where an orthogonal cover code (OCC)sequence of 4 bits may be applied to two pairs of two consecutivereference symbols, for example to separate multiple RSs, for example, onantenna port 7 and 8.

It may be assumed that DM-RS based channel estimation for datademodulation operates on a per subframe basis (e.g., no interpolationtechnique is used between adjacent subframes for channel estimation).Accordingly, channel estimation for OFDM symbols prior to the sixth OFDMsymbol in the first timeslot in a subframe may be carried out using someform of extrapolation based channel estimation. However extrapolationbased channel estimation may cause performance of the PDSCH to bedegraded. In extension carriers and/or carrier segments, the PDSCH maystart from the first OFDM symbol in the first timeslot.

Use of extrapolation based channel estimation in extension carriersand/or carrier segments, which may be collectively referred to asextension resource carriers, may be avoided. For example, mapping of REsto OFDM symbols for DM-RS in extension resource carriers, which may bereferred to as extension DM-RS structure and/or mapping (e.g. in thefirst timeslot in a subframe), may include mapping DM-RSs to REpositions that may correspond to earlier OFDM symbols (e.g., REs usedfor the PDCCH and/or CRS in LTE R10). Any suitable component of acommunications system may be configured to employ extension DM-RSstructure and/or mapping (e.g., a UE, a component of a CN, or the like).

Referring now to FIG. 5, in accordance with an example of extensionDM-RS structure and/or mapping, DM-RSs for antenna ports A and B (e.g.,antenna ports 7 and 8 of a corresponding UE with normal CP) may bepositioned in (e.g., inserted into, appended to, etc.) REs in one ormore respective OFDM symbols (e.g., RE1 and RE2) in the first timeslot(e.g., TS1) of at least one subcarrier (e.g., SC 2, SC 7, and/or SC12).The DM-RSs may be positioned in the first timeslot at any time relativeto transmission of the subcarrier (e.g., prior to transmission,substantially at the time of transmission, etc.). The subcarrier may betransmitted by any suitable component of a communication system (e.g.,by an eNB).

In this regard, extension DM-RS structure and/or mapping may includetransmitting a first timeslot (e.g., TS1) of a subcarrier (e.g., SC2).The first timeslot may have a first plurality of resource elements thatare ordered from a first resource element to a last resource element(e.g., RE1-RE7). Transmitting the first timeslot may includetransmitting a first symbol in a select one of the first plurality ofresource elements (e.g., RE1) that may not be the last resource element.The first symbol may be a demodulation reference signal (e.g., aUE-specific DM-RS). Transmitting the first timeslot may includetransmitting a second symbol in the last resource element of the firstplurality of resource elements (e.g., RE7), wherein the second symbol isother than a demodulation reference signal (e.g., not a UE-specificDM-RS). For example, the second symbol may include OFDM symbolscomprising voice and/or data information. Transmitting the firsttimeslot may include transmitting a third symbol in a second select oneof the first plurality of resource elements (e.g., RE2) that may not bethe last resource element. The third symbol may be a demodulationreference signal (e.g., a UE-specific DM-RS).

In accordance with the illustrated example of extension DM-RS structureand/or mapping, the first and second select ones of the plurality ofresource elements (e.g., RE1 and RE2), respectively, may be adjacent toone another in the first timeslot.

Further in accordance with the illustrated example of extension DM-RSstructure and/or mapping, DM-RSs for antenna ports A and B (e.g.,antenna ports 7 and 8 of a corresponding UE with normal CP) may bepositioned in REs in one or more respective OFDM symbols (e.g., RE6 andRE7) in the second timeslot (e.g., TS2) of at least one subcarrier(e.g., SC 2, SC 7, and/or SC12).

In this regard, extension DM-RS structure and/or mapping may includetransmitting a second timeslot (e.g., TS2) of the subcarrier (e.g.,SC2). The second timeslot may have a second plurality of resourceelements that are ordered from a first resource element to a lastresource element (e.g., RE1-RE7). Transmitting the second timeslot mayinclude transmitting a fourth symbol in a select one of the secondplurality of resource elements (e.g., RE6). The fourth symbol may be ademodulation reference signal (e.g., a UE-specific DM-RS). Transmittingthe second timeslot may include transmitting a fifth symbol in a selectone of the second plurality of resource elements (e.g., RE7). The fifthsymbol may be a demodulation reference signal (e.g., a UE-specificDM-RS).

The UE-specific DM-RSs of the first and second timeslots may be locatedin different RE locations (e.g., RE1 and RE2 of TS1 and RE6 and RE7 ofTS2). The UE-specific DM-RSs of the first timeslot (e.g., TS1) may belocated in a first position relative to the plurality of resourceelements of the first timeslot (which may be referred to as a firstplurality of reference elements) and the UE-specific DM-RSs of thesecond timeslot may be located in a second position relative to thesecond plurality of resource elements of the second timeslot TS2, suchthat the first position may be different relative to the first position.In this regard, the first symbol and the third symbol may be located indifferent positions relative to the first and second pluralities ofresource elements, respectively.

In the illustrated example of extension DM-RS structure and/or mapping,an interval between two pairs of consecutive reference symbols (e.g., intime) within a subframe may be longer with respect to the DM-RSstructure illustrated in FIG. 4. However the illustrated extension DM-RSstructure and/or mapping may enable interpolation-based channelestimation (e.g., for PDSCH demodulation to be carried out).

FIG. 6 depicts another example of extension DM-RS structure and/ormapping for antenna ports A and B (e.g., antenna ports 7 and 8 of acorresponding UE with normal CP). In accordance with the illustratedexample, DM-RSs may be positioned in (e.g., inserted into, appended to,etc.) REs in one or more respective OFDM symbols (e.g., RE3 and RE4) inthe first timeslot (e.g., TS1) and REs in one or more respective OFDMsymbols (e.g., RE4 and RE5) in the second timeslot (e.g., TS2) of atleast one subcarrier (e.g., SC 2, SC 7, and SC12). The illustratedextension DM-RS structure and/or mapping may enable interpolation basedchannel estimation (e.g., for PDSCH demodulation to be carried out).

FIG. 7 depicts another example of extension DM-RS structure and/ormapping for antenna ports A and B (e.g., antenna ports 7 and 8 of acorresponding UE with normal CP). In accordance with the illustratedexample, DM-RSs may be positioned in (e.g., inserted into, appended to,etc.) REs in one or more respective OFDM symbols (e.g., RE1 and RE2) inthe first timeslot (e.g., TS1) of a first subcarrier (e.g., SC2) and REsin one or more respective OFDM symbols (e.g., RE6 and RE7) in the secondtimeslot (e.g., TS2) of the first subcarrier. In a second subcarrier(e.g., SC 7) DM-RSs may be positioned in different OFDM symbol locationsthan in the first subcarrier. For example, DM-RSs may be positioned inREs in one or more respective OFDM symbols (e.g., RE5 and RE6) in thefirst timeslot (e.g., TS1) and in REs in one or more respective OFDMsymbols (e.g., RE2 and RE3) in the second timeslot (e.g., TS2) of thesecond subcarrier.

In this regard, extension DM-RS structure and/or mapping may includetransmitting a first timeslot (e.g., TS1) of a first subcarrier (e.g.,SC2). The first timeslot of the first subcarrier may have a firstplurality of resource elements that are ordered from a first resourceelement to a last resource element (e.g., RE1-RE7). Transmitting thefirst timeslot of the first subcarrier may include transmitting a firstsymbol in a select one of the first plurality of resource elements(e.g., RE1) that may not be the last resource element. The first symbolmay be a demodulation reference signal (e.g., a UE-specific DM-RS).Transmitting the first timeslot of the first subcarrier may includetransmitting a second symbol in the last resource element of the firstplurality of resource elements (e.g., RE7), wherein the second symbol isother than a demodulation reference signal (e.g., not a UE-specificDM-RS). For example, the second symbol may include OFDM symbolscomprising voice and/or data information.

In accordance with the illustrated example, extension DM-RS structureand/or mapping may include transmitting a first timeslot of a secondsubcarrier (e.g., SC 7). The first timeslot of the second subcarrier mayhave a plurality of resource elements (which may be referred to as asecond plurality of resource elements) that are ordered from a firstresource element to a last resource element (e.g., RE1-RE7).Transmitting the first timeslot of the second subcarrier may includetransmitting a third symbol in a select one of the second plurality ofresource elements (e.g., RE5) of the first timeslot of the secondsubcarrier. The third symbol may be a demodulation reference signal(e.g., a UE-specific DM-RS). Transmitting the first timeslot of thesecond subcarrier may include transmitting a fourth symbol in the lastresource element of the second plurality of resource elements (e.g.,RE7), wherein the fourth symbol is other than a demodulation referencesignal (e.g., not a UE-specific DM-RS). For example, the fourth symbolmay include OFDM symbols comprising voice and/or data information.

In a third subcarrier (e.g., SC 12) DM-RSs may be positioned indifferent OFDM symbol locations than in the second subcarrier. Forexample, DM-RSs may be positioned in REs in one or more respective OFDMsymbols (e.g., RE1 and RE2) in the first timeslot (e.g., TS1) of thethird subcarrier and in REs in one or more respective OFDM symbols(e.g., RE6 and RE7) in the second timeslot (e.g., TS2) of the thirdsubcarrier. In this regard, the DM-RS symbols of the third subcarriermay be located in substantially the same locations relative to the DM-RSsymbols of the first subcarrier. The first, second, and thirdsubcarriers may be staggered with respect to each other, such that atleast one subcarrier that may not have DM-RSs may disposed between thefirst and second subcarriers and/or at least one other subcarrier thatmay not have DM-RS symbols may be disposed between the second and thirdsubcarriers.

The UE-specific DM-RSs of the first and second subcarriers (e.g., SC2and SC7) may be located in different RE locations (e.g., RE1 and RE2 ofSC12 and RE5 and RE6 of SC7), the UE-specific DM-RSs of the firstsubcarrier may be located in a first position relative to the pluralityof resource elements of the first timeslot TS1 of the first subcarrier(which may be referred to as a first plurality of reference elements)and the UE-specific DM-RSs of the second subcarrier may be located in asecond position relative to the second plurality of resource elements ofthe first timeslot of the second subcarrier, such that the firstposition may be different relative to the first position. In thisregard, the first symbol and the third symbol may be located indifferent positions relative to the first and second pluralities ofresource elements, respectively. The UE-specific DM-RS symbols of thefirst subcarrier and the UE-specific DM-RS symbols of the secondsubcarrier may be located in different positions relative to the firstand second pluralities of resource elements, respectively. TheUE-specific DM-RS symbols of the second subcarrier and the UE-specificDM-RS symbols of the third subcarrier may be located in differentpositions relative to the respective pluralities of resource elements offirst timeslots of the second and third subcarriers. The UE-specificDM-RS symbols of the first subcarrier and the UE-specific DM-RS symbolsof the third subcarrier may be located in substantially the samepositions relative to the respective pluralities of resource elements offirst timeslots of the first and third subcarriers.

With continuing reference to FIG. 7, the illustrated extension DM-RSstructure and/or mapping may comprise a pair-wise time-domain staggeringof N OFDM symbols within a subframe. Pair-wise time-domain staggeringmay provide accurate channel estimation and/or measurements whenchannels vary non-monotonically in both time and frequency domains(e.g., channel peak or sink occurs in the middle of the RB). Afrequency-domain staggering of M subcarriers for the RS within a RBand/or a subframe may be applied. A combination of time-domainstaggering and frequency-domain staggering may be applied.

In the examples of extension DM-RS structure and/or mapping depicted inFIGS. 5-7, DM-RSs may be positioned in REs in two consecutive OFDMsymbols (in time) (e.g., RE1 and RE2 in FIG. 5) in each timeslot in asubframe. The consecutive OFDM symbols may be paired. Two pairs ofconsecutive reference symbols (e.g., four reference symbols in a singlesubcarrier) in a subframe may be covered (e.g., spread and/ormultiplied) by a 4-bit OCC sequence, so that Extension DM-RSs formultiple antenna ports (e.g., antenna ports 7 and 8) may be separated(e.g., using CDM in the receiver). Alternatively, a set of the OCCsequences (e.g., OCC sequences used for LTE R10 DM-RS) may be appliedfor extension DM-RS structure and/or mapping (e.g., as depicted in shownin FIGS. 5-7).

FIG. 8 depicts another example of extension DM-RS structure and/ormapping for antenna ports A and B (e.g., antenna ports 7 and 8 of acorresponding UE with normal CP). In accordance with the illustratedexample, DM-RSs may be separated from each other by one or morenon-DM-RS OFDM symbols, such that no two DM-RSs are consecutive in time.For example, DM-RSs may be positioned in (e.g., inserted into, appendedto, etc.) REs in one or more respective OFDM symbols (e.g., RE1 and RE5)in the first timeslot (e.g., TS1) of at least one subcarrier (e.g., SC2,SC7, and SC12) and in REs in one or more respective OFDM symbols (e.g.,RE2 and RE7) in the second timeslot (e.g., TS2) of the at least onesubcarrier. In this regard, first and second select ones of a firstplurality of resource elements of the first timeslot that carryrespective DM-RSs (e.g., RE1 and RE5) respectively, are spaced apartfrom one another in the first timeslot, and first and second select onesof a second plurality of resource elements of the second timeslot thatcarry respective DM-RSs (e.g., RE2 and RE7) respectively, are spacedapart from one another in the second timeslot.

The illustrated example of extension DM-RS structure and/or mapping mayprovide channel estimation using an interpolation technique. Because thefour DM-RSs symbols are not consecutive in time, a DM-RS orthogonalityproperty might not be maintained in, for example, fast varying channelconditions (e.g., for high mobility UEs).

FIGS. 9A-B depicts an example of extension DM-RS structure and/ormapping for multiple antenna ports A, B, C, and D (e.g., antenna ports7, 8, 9, and 10 of a corresponding UE with normal CP). In accordancewith the illustrated example, DM-RSs for antenna port A may bepositioned in (e.g., inserted into, appended to, etc.) REs in one ormore respective OFDM symbols (e.g., RE5) in the first timeslot (e.g.,TS1) of at least one subcarrier (e.g., SC4 and SC10) and in REs in oneor more respective OFDM symbols (e.g., RE5) in the second timeslot(e.g., TS2) of the at least one subcarrier. The first and secondsubcarriers may be staggered with respect to each other. DM-RSs forantenna port B may be positioned in REs in one or more respective OFDMsymbols (e.g., RE1) in the first timeslot (e.g., TS1) of a firstsubcarrier (e.g., SC1) and in REs in one or more respective OFDM symbols(e.g., RE1) in the second timeslot (e.g., TS2) of the first subcarrierand may be positioned in REs in one or more respective OFDM symbols(e.g., RE5) in the first timeslot (e.g., TS1) of a second subcarrier(e.g., SC10) and in REs in one or more respective OFDM symbols (e.g.,RE5) in the second timeslot (e.g., TS2) of the second subcarrier. Thefirst and second subcarriers may be staggered with respect to eachother.

In this regard, extension DM-RS structure and/or mapping may includetransmitting a first timeslot (e.g., TS1) of a subcarrier (e.g., SC4).The first timeslot may have a first plurality of resource elements thatare ordered from a first resource element to a last resource element(e.g., RE1-RE7). Transmitting the first timeslot may includetransmitting a first symbol in a select one of the first plurality ofresource elements (e.g., RE5) that may not be the last resource element.The first symbol may be a demodulation reference signal (e.g., aUE-specific DM-RS). Transmitting the first timeslot may includetransmitting a second symbol in the last resource element of the firstplurality of resource elements (e.g., RE7), wherein the second symbol isother than a demodulation reference signal (e.g., not a UE-specificDM-RS).

Extension DM-RS structure and/or mapping may include transmitting asecond timeslot (e.g., TS2) of the subcarrier (e.g., SC4). The secondtimeslot may have a second plurality of resource elements that areordered from a first resource element to a last resource element (e.g.,RE1-RE7). Transmitting the second timeslot may include transmitting athird symbol in a select one of the second plurality of resourceelements (e.g., RE5). The third symbol may be a demodulation referencesignal (e.g., a UE-specific DM-RS).

The UE-specific DM-RSs of the first and second timeslots may be locatedin substantially the same locations relative to their respectivepluralities of reference elements (e.g., RE5 of TS1 and RE5 of TS2).Stated differently, the UE-specific DM-RS of the first timeslot may belocated in a first position relative to the plurality of resourceelements of the first timeslot TS1 (which may be referred to as a firstplurality of reference elements) and the UE-specific DM-RS of the secondtimeslot may be located in a second position relative to the secondplurality of resource elements of the second timeslot TS2, such that thefirst position may be substantially the same relative to the firstposition. In this regard, the first symbol and the third symbol may belocated in substantially equivalent positions relative to the first andsecond pluralities of resource elements, respectively.

Transmitting a first timeslot of a second subcarrier (e.g., SC 10) mayinclude transmitting a fourth symbol in a select one of a firstplurality of resource elements (e.g., RE5) of the first timeslot of thesecond subcarrier. The fourth symbol may be a demodulation referencesignal (e.g., a UE-specific DM-RS). Transmitting a second timeslot ofthe second subcarrier (e.g., SC 10) may include transmitting a fifthsymbol in a select one of a second plurality of resource elements (e.g.,RE5) of the second timeslot of the second subcarrier. The fifth symbolmay be a demodulation reference signal (e.g., a UE-specific DM-RS).

Further in accordance with the illustrated example of extension DM-RSstructure and/or mapping, overhead of DM-RS may be limited (e.g., inPDSCH transmission on an extension carrier and/or carrier segments). Forexample, extension DM-RS structure and/or mapping for one or moreantenna ports (e.g., antenna ports 9 and 10) may be transmitted using alower DM-RS density in the time and/or the frequency domains. Forexample, DM-RSs for antenna port C may be positioned in REs in one ormore respective OFDM symbols (e.g., RE2) in the first timeslot (e.g.,TS1) of a first subcarrier (e.g., SC 1) and may be positioned in REs inone or more respective OFDM symbols (e.g., RE2) in the second timeslot(e.g., TS2) of a second subcarrier (e.g., SC10). The first and secondsubcarriers may be staggered with respect to each other. DM-RSs forantenna port D may be positioned in REs in one or more respective OFDMsymbols (e.g., RE2) in the first timeslot (e.g., TS1) of a firstsubcarrier (e.g., SC 10) and may be positioned in REs in one or morerespective OFDM symbols (e.g., RE2) in the second timeslot (e.g., TS2)of a second subcarrier (e.g., SC1). The first and second subcarriers maybe staggered with respect to each other.

It should be appreciated that extension DM-RS (e.g., UE-specific DM-RS)structure and/or mapping is not limited to the examples illustrated anddescribed herein, and that extension DM-RS structure and/or mapping mayinclude any other combinations of DS-RSs varied in one or both of thetime and frequency domains (e.g., using the RE resource grid).

One or more (e.g., all) of the herein disclosed extension DM-RSstructure and/or mapping examples, configurations, and/or patterns maybe used to configure UEs. UEs may be configured with any of the set(e.g., all) of the Extension DM-RS structure and/or mappingconfigurations and/or patterns. For example, a UE (e.g., in response tobeing configured with extension carriers and/or carrier segments) may beconfigured with any of the set (e.g., all) of the Extension DM-RSstructure and/or mapping configurations and/or patterns (e.g., via L1signaling and/or L2/3 signaling). A UE previously configured withextension carriers and/or carrier segments and/or any of the extensionDM-RS structure and/or mapping configurations and/or patterns may bereconfigured with any of the set (e.g., all) of the extension DM-RSstructure and/or mapping configurations and/or patterns via L1 signalingand/or L2/3 signaling.

Extension DM-RS structure and/or mapping configurations and/or patternsmay be configured per UE and/or per extension carrier and/or carriersegment. DM-RSs may be transmitted only in RBs upon which acorresponding PDSCH is mapped. The configuration may depend on the CPtype (e.g., normal CP vs. extended CP). For example, as defined in TS36.211, for antenna ports p=7, 8, or p=7, 8, . . . , v+6, in a PRB withfrequency-domain index, n_(PRB), assigned for s corresponding PDSCH, apart of the reference sequence r(m) may be mapped to complex-valuedmodulation symbols, a_(k,l), in a subframe as follows:

Normal Cyclic Prefix:

a_(k, l)^((p)) = w_(p)(l^(′)) ⋅ r(3 ⋅ l^(′) ⋅ N_(RB)^(max , DL) + 3 ⋅ n_(PRB) + m^(′))where ${w_{p}(i)} = \left\{ {{\begin{matrix}{{\overset{\_}{w}}_{p}(i)} & {{\left( {m^{\prime} + n_{PRB}} \right){mod}\; 2} = 0} \\{{\overset{\_}{w}}_{p}\left( {3 - i} \right)} & {{\left( {m^{\prime} + n_{PRB}} \right){mod}\; 2} = 1}\end{matrix}k} = {{{5\; m^{\prime}} + {N_{sc}^{RB}n_{PRB}} + {k^{\prime}k^{\prime}}} = \left\{ {{\begin{matrix}1 & {p \in \left\{ {7,8,11,13} \right\}} \\0 & {p \in \left\{ {9,10,12,14} \right\}}\end{matrix}l} = \left\{ {{\begin{matrix}{{l^{\prime}{mod}\; 2} + 2} & {{{if}\mspace{14mu} {in}\mspace{14mu} a\mspace{14mu} {special}\mspace{14mu} {subframe}\mspace{14mu} {with}\mspace{14mu} {configuration}\mspace{14mu} 3},4,{{or}\mspace{14mu} 8\left( {{see}\mspace{14mu} {Table}\mspace{14mu} 4.2\text{-}1} \right)}} \\{{l^{\prime}{mod}\; 2} + 2 + {3\left\lfloor {l^{\prime}/2} \right\rfloor}} & {{{if}\mspace{14mu} {in}\mspace{14mu} a\mspace{14mu} {special}\mspace{14mu} {subframe}\mspace{14mu} {with}\mspace{14mu} {configuration}\mspace{14mu} 1},2,6,{{or}\mspace{14mu} 7\left( {{see}\mspace{14mu} {Table}\mspace{14mu} 4.2\text{-}1} \right)}} \\{{l^{\prime}{mod}\; 2} + 5} & {{if}\mspace{14mu} {not}\mspace{14mu} {in}\mspace{14mu} a\mspace{14mu} {special}\mspace{14mu} {subframe}}\end{matrix}l^{\prime}} = \left\{ {{{\begin{matrix}{0,1,2,3} & {{{{if}\mspace{14mu} n_{s}{mod}\; 2} = {0\mspace{14mu} {and}\mspace{20mu} {in}\mspace{14mu} a\mspace{14mu} {special}\mspace{14mu} {subframe}\mspace{14mu} {with}\mspace{14mu} {configuration}\mspace{14mu} 1}},2,6,{{or}\mspace{14mu} 7\left( {{see}\mspace{14mu} {Table}\mspace{14mu} 4.2\text{-}1} \right)}} \\{0,1} & {{{{if}\mspace{14mu} n_{s}{mod}\; 2} = {0\mspace{14mu} {and}\mspace{14mu} {not}\mspace{14mu} {in}\mspace{14mu} {special}\mspace{14mu} {subframe}\mspace{14mu} {with}\mspace{14mu} {configuration}\mspace{14mu} 1}},2,6,{{or}\mspace{14mu} 7\left( {{see}\mspace{14mu} {Table}\mspace{14mu} 4.2\text{-}1} \right)}} \\{2,3} & {{{{if}\mspace{14mu} n_{s}{mod}\; 2} = {1\mspace{14mu} {and}\mspace{14mu} {not}\mspace{14mu} {in}\mspace{14mu} {special}\mspace{14mu} {subframe}\mspace{14mu} {with}\mspace{14mu} {configuration}\mspace{14mu} 1}},2,6,{{or}\mspace{14mu} 7\left( {{see}\mspace{14mu} {Table}\mspace{14mu} 4.2\text{-}1} \right)}}\end{matrix}m^{\prime}} = 0},1,2} \right.} \right.} \right.}} \right.$

The OCC sequence w _(p)(i) may be found, for example, in TS. 36.211.

In the above DM-RS mapping equation, the OFDM symbol index, l (and l′),may be configured for each UE and/or for each extension carrier (e.g.,all) extension carriers. For example, for the extension DM-RS structureand/or mapping depicted in FIG. 5, l (and l′) may be modified fornon-special subframes (e.g., FDD) as follows:

l=l′ mod 2, l′=0,1 if n _(s) mod 2=0

l=l′ mod 2+5, l′=2,3 if n _(s) mod 2=1

For the extension DM-RS structure and/or mapping depicted in FIG. 6,

l = l^(′)mod 2 + 2 $l^{\prime} = \left\{ \begin{matrix}{0,1} & {{{if}\mspace{14mu} n_{s}{mod}\; 2} = 0} \\{2,3} & {{{if}\mspace{14mu} n_{s}{mod}\; 2} = 1}\end{matrix} \right.$

For the Extension DM-RS structure and/or mapping depicted in FIG. 6,

if m′=0 or 2

l=l′ mod 2, l′=0,1 if n _(s) mod 2=0

l=l′ mod 2+5, l′=2,3 if n _(s) mod 2=1

else (e.g., if m′=1)

l=l′ mod 2+4, l′=0,1 if n _(s) mod 2=0

l=l′ mod 2+1, l′=2,3 if n _(s) mod 2=1

For extended CP, respective modification rules that may be substantiallythe same as those for normal CP may be applied. However different CPtypes may require one or more different rules for modifying one or morecorresponding extension DM-RS structures and/or mappings.

In addition to extension DM-RS structure and/or mapping, the followingDM-RS related parameters and/or variables may be configured and/ormodified for extension DM-RS structure and/or mapping. OCC sequences(e.g., wp(l)) may be configured and/or modified (e.g., for all DM-RSs),including, for example, DM-RSs that are not consecutive in the timedomain. Different sets and/or tables of the OCC sequences may be definedfor different DM-RS structures and/or mappings. For each antenna port, p(e.g. in LTE R10), the OCC sequences and the order of their elements maybe the same for three different subcarriers/REs (e.g., m′=0, 1 or 2) inan RB as shown in the expression of

a _(k,l) ^((p)) =w _(p)(l′)·r(3·l′·N _(RB) ^(max,DL)+3·n _(PRB) +m′).

Channel estimation from de-spreading of OCC at the receiver may onlytake place along the time domain for each of three subcarriers where theDM-RS symbols reside. Channel estimation of other frequency-timelocation within the RB may be done by interpolation and/or extrapolation(e.g., from those three estimations). The channel estimation based onthis method may not be accurate for channels varying in both the timedomain and the frequency domain within a RB.

For extension DM-RS structure and/or mapping, the order of the OCCsequence may be changed in the middle subcarrier (e.g., m′=1) such thatde-spreading over both the frequency domain and the time domain may bepossible. Accordingly, for normal cyclic prefix:

a_(k, l)^((p)) = w_(p)(l^(″)) ⋅ r(3 ⋅ l^(″) ⋅ N_(RB)^(max , DL) + 3 ⋅ n_(PRB) + m^(′))where ${w_{p}(i)} = \left\{ {{\begin{matrix}{{\overset{\_}{w}}_{p}(i)} & {{\left( {m^{\prime} + n_{PRB}} \right){mod}\; 2} = 0} \\{{\overset{\_}{w}}_{p}\left( {3 - i} \right)} & {{\left( {m^{\prime} + n_{PRB}} \right){mod}\; 2} = 1}\end{matrix}k} = {{{5\; m^{\prime}} + {N_{sc}^{RB}n_{PRB}} + {k^{\prime}k^{\prime}}} = \left\{ {{\begin{matrix}1 & {p \in \left\{ {7,8,11,13} \right\}} \\0 & {p \in \left\{ {9,10,12,14} \right\}}\end{matrix}l} = \left\{ {{\begin{matrix}{{l^{\prime}{mod}\; 2} + 2} & {{{if}\mspace{14mu} {in}\mspace{14mu} a\mspace{14mu} {special}\mspace{14mu} {subframe}\mspace{14mu} {with}\mspace{14mu} {configuration}\mspace{14mu} 3},4,{{or}\mspace{14mu} 8\left( {{see}\mspace{14mu} {Table}\mspace{14mu} 4.2\text{-}1} \right)}} \\{{l^{\prime}{mod}\; 2} + 2 + {3\left\lfloor {l^{\prime}/2} \right\rfloor}} & {{{if}\mspace{14mu} {in}\mspace{14mu} a\mspace{14mu} {special}\mspace{14mu} {subframe}\mspace{14mu} {with}\mspace{14mu} {configuration}\mspace{14mu} 1},2,6,{{or}\mspace{14mu} 7\left( {{see}\mspace{14mu} {Table}\mspace{14mu} 4.2\text{-}1} \right)}} \\{{l^{\prime}{mod}\; 2} + 5} & {{if}\mspace{14mu} {not}\mspace{14mu} {in}\mspace{14mu} a\mspace{14mu} {special}\mspace{14mu} {subframe}}\end{matrix}l^{\prime}} = \left\{ {{\begin{matrix}{0,1,2,3} & {{{{if}\mspace{14mu} n_{s}{mod}\; 2} = {0\mspace{14mu} {and}\mspace{20mu} {in}\mspace{14mu} a\mspace{14mu} {special}\mspace{14mu} {subframe}\mspace{14mu} {with}\mspace{14mu} {configuration}\mspace{14mu} 1}},2,6,{{or}\mspace{14mu} 7\left( {{see}\mspace{14mu} {Table}\mspace{14mu} 4.2\text{-}1} \right)}} \\{0,1} & {{{{if}\mspace{14mu} n_{s}{mod}\; 2} = {0\mspace{14mu} {and}\mspace{14mu} {not}\mspace{14mu} {in}\mspace{14mu} {special}\mspace{14mu} {subframe}\mspace{14mu} {with}\mspace{14mu} {configuration}\mspace{14mu} 1}},2,6,{{or}\mspace{14mu} 7\left( {{see}\mspace{14mu} {Table}\mspace{14mu} 4.2\text{-}1} \right)}} \\{2,3} & {{{{if}\mspace{14mu} n_{s}{mod}\; 2} = {1\mspace{14mu} {and}\mspace{14mu} {not}\mspace{14mu} {in}\mspace{14mu} {special}\mspace{14mu} {subframe}\mspace{14mu} {with}\mspace{14mu} {configuration}\mspace{14mu} 1}},2,6,{{or}\mspace{14mu} 7\left( {{see}\mspace{14mu} {Table}\mspace{14mu} 4.2\text{-}1} \right)}}\end{matrix}l^{''}} = \left\{ {{{\begin{matrix}l^{\prime} & {{{{if}\mspace{14mu} m^{\prime}} = 0},2} \\{{\left( {l^{\prime} + 2} \right){mod}\; 4},} & {{{if}\mspace{14mu} m^{\prime}} = 1}\end{matrix}m^{\prime}} = 0},1,2} \right.} \right.} \right.} \right.}} \right.$

FIG. 10 depicts an example OCC distribution for Extension DM-RS, whichmay be referred to as an Extension OCC Distribution. The Extension OCCDistribution may be a modification of OCC sequence distribution (e.g.,using the example extension DM-RS structure and/or mapping depicted inFIG. 7. Seven different channel estimation values based on de-spreadingof the OCC may be obtained. The channel estimation values may be used torepresent channels in seven different time-frequency locations within aRB. A two dimensional interpolation and/or extrapolation may be used toobtain a channel estimation for any RE within the RB.

For reference signal (RS) mapping in the frequency domain, a mappingpattern in the frequency domain of the reference signal sequence r(m)may be modified (e.g., using subcarrier index, k, in the RS to REmapping equation). For example,

a _(k,l) ^((p)) =w _(p)(l′)·r(3·l′·N _(RB) ^(max,DL)+3·n _(PRB) +m′).

for antenna ports p=7, p=8, or p=7, 8, . . . , v+6, and normal CP wherek may be determined for the above mapping equation as:

k = 5 m^(′) + n_(sc)^(RB)n_(PRB) + k^(′)$k^{\prime} = \left\{ \begin{matrix}1 & {p \in \left\{ {7,8,11,13} \right\}} \\0 & {p \in \left\{ {9,10,12,14} \right\}}\end{matrix} \right.$

For extension carriers and/or carrier segments, k may be modified, forexample for frequency hopping such that frequency hopping of the set of,or a subset of, subcarriers used for the DM-RS transmission for a givenUE may be performed on a subframe and/or radio frame basis. Frequencyhopping for the DM-RS transmission may be configured (e.g., includingenable and/or disable) per extension carrier and/or carrier segmentand/or per UE.

For antenna port 5, for other antenna ports (e.g., port 7, 8, . . . ,v+6), the cell-specific (or UE-specific) frequency shift, v_(shift), maybe included in k, for example,

k = 5 m^(′) + n_(sc)^(RB)n_(PRB) + k^(′)$k^{\prime} = \left\{ \begin{matrix}{1 + v_{shift}^{1}} & {p \in \left\{ {7,8,11,13} \right\}} \\{0 + v_{shift}^{2}} & {p \in \left\{ {9,10,12,14} \right\}}\end{matrix} \right.$

where v_(shift) ¹ and v_(shift) ² may be cell-specific and/orUE-specific frequency shifts, may be a function of the cell-ID and/or UEID, and/or may be set to a same value. For antenna port 5 (e.g., TM 5),the cell-specific frequency shift, v_(shift), may be modified.

DM-RS performance may be improved. For example, the density of extensionDM-RS may be increased by increasing the number of OFDM symbols used forDM-RS transmission, by increasing the number of REs mapped for the DM-RSin a RB, and/or by increasing both the number of OFDM symbols and thenumber of REs.

In order to reduce DM-RS overhead (e.g., for extension carriers and/orcarrier segments, the density of Extension DM-RS may get lower in thetime domain and/or the frequency domain (e.g., as depicted in FIGS.9A-B).

In an MBSFN subframe, if a PDSCH for a given UE is transmitted in thecarrier segments configured for a serving cell, the Extension DM-RS maybe transmitted as in the corresponding carrier segments of a non-MBSFNsubframe. The extension DM-RS defined for extended CP may be used forthe carrier segments.

DM-RS transmission may be configured per extension carrier and/or perWTRU (e.g., depending upon the TM configured for the extension carrier).DM-RS transmission may be configured per carrier segments of a servingcell and/or per UE (e.g., depending on the TM configured for the carriersegments).

Extension DM-RS (e.g., UE-specific DM-RS structure and/or mapping) maybe used when the use of extension carrier and/or carrier segments isconfigured for a UE and/or when extension DM-RS is activated for a UE.

CRS may be used for several purposes in extension carriers and/orcarrier segments, including data demodulation, for example, for TM 1˜6,and/or CQI reporting for TM 1˜8. CRS may be used for assistingsynchronization operation at a UE.

CRS may be transmitted on extension carrier and/or carrier segments whenthe extension carrier and/or carrier segments are configured, and/orwhen the extension carrier and/or carrier segments are activated.

CRS may be transmitted on extension carrier and/or carrier segments, forexample so that a UE configured with extension carriers and/or carriersegments may perform measurements based on CRS, for example, to acquireCSI and/or carrier-specific time and/or frequency tracking and/orsynchronization.

CSI-RS may be transmitted on extension carriers and/or carrier segments.For example, a UE may be configured with an extension carrier and/orcarrier segments of a serving cell. If the UE is configured with a TMcapable of supporting CSI-RS (e.g., TM 9) on the extension carrierand/or carrier segments, then CSI for the UE may be transmitted on theextension carrier. Examples of configuring CRS for extension carriersand/or carrier segments may be described herein.

A CRS (e.g., the structure thereof) in an extension carrier and/orcarrier segment may include fewer OFDM symbols used for CRS transmissionin a subframe than the number of OFDM symbols that may be used a primarycarrier CRS structure (e.g., a CRS in LTE R10).

FIGS. 11-13 depict example CRS mappings and/or configurations forimplementing CRSs (depicted as CS in the FIGS.) in extension carriersand/or carrier segments. The example mappings and/or configurations aredepicted in terms of respective numbers of OFDM symbols that may beoccupied with CRS in a subframe (e.g., using four antenna ports andnormal CP).

In the example CRS mapping and/or configuration depicted in FIG. 12,CRSs may be transmitted only in the second timeslot (e.g., TS2) in asubframe, which may result in approximately a 50% CRS overhead reduction(e.g., relative to LTE R10). The number of REs used for CRS transmissionper RB may be configured for each antenna port and/or for some of theantenna ports. For example, antenna ports 0 and 1 may be configured touse 4 REs per RB for CRS transmission and antenna ports 2 and 3 may beconfigured to use 2 REs per RB for CRS transmission. A CRS configurationmay be provided for one or more UEs configured with an extension carrierand/or carrier segment (e.g., via RRC signaling and/or broadcastsignaling). Configuration signaling may be provided from a serving celllinked to the extension carrier and/or from a PCell.

For extension carriers and/or carrier segments, CRS transmission with alower density in the time domain and/or the frequency domain may performsome UE measurements, for example CQI reporting, timing tracking and/orsynchronization, and/or frequency tracking and/or synchronization.

CRS may be configured to be transmitted only in certain subframes in anextension carrier and/or carrier segment (e.g. in certain subframes ofone or more radio frames in an extension carrier and/or carriersegment). For example, the periodicity of CRS transmission may beconfigured for an extension carrier and/or carrier segment and may beprovided for one or more UEs configured with the extension carrierand/or carrier segment (e.g., via RRC signaling and/or broadcastsignaling). The periodicity may comprise a parameter of a configurationreceived by the one or more UEs. The parameter may indicate theperiodicity of subframes that carry CRS. The configuration signaling maybe provided from a serving cell linked to the extension carrier and/orfrom a PCell. One or more extension carriers and/or carrier segments maybe configured not to carry CRS (e.g., by setting the periodicity of CRStransmission on the carrier to an infinite value and/or by setting aparameter for the carrier).

Transmission subframes and/or antenna ports for CRS may be configuredsimilarly CSI-RS, for example to reduce overhead.

CRS transmission on an extension carrier and/or carrier segment may beconfigured dependent on the transmission mode, or modes, that theextension carrier and/or carrier segment may support. For example, ifthe extension carrier and/or carrier segment supports only TM9, thenExtension CRS may not be transmitted on the carrier. In accordance withanother example, if the extension carrier and/or carrier segmentsupports multiple TMs, then CRS may be configured to be transmitted onthe extension carrier and/or carrier segment. Configuration signalingmay be provided from a serving cell linked to the extension carrier.

The number of antenna ports for the Extension CRS transmission may beconfigured for each extension carrier and/or carrier segment. Theantenna configuration may be provided to one or more UEs configured withthe extension carrier and/or carrier segment (e.g., via RRC signalingand/or broadcast signaling). The configuration signaling may be providedfrom a serving cell linked to the extension carrier and/or from a PCell.An antenna configuration for the CRS transmission on the carrier may beindependent of that for DM-RS and/or CSI-RS on the same carrier. A setof antenna ports for CRS transmission may be limited, for example toonly two antenna ports (e.g. antenna ports 0 and 1), for extensioncarriers and/or carrier segments. The antenna configuration for thelinked serving cell and/or the PCell may be applied to one or moreextension carriers and/or carrier segments.

Rather than transmitting CRS over an entirety of the bandwidth of anextension carrier and/or carrier segment, CRS for the carrier may betransmitted only on a limited set of RBs (e.g., including RBs upon whichone or more corresponding PDSCHs for a UE or a group of UEs configuredwith the carrier may be mapped). The bandwidth in which the ExtensionCRS may be transmitted may be configured and/or provided for the UE, orgroup of UEs (e.g., via RRC signaling and/or broadcast signaling fromthe serving cell linked to the extension carrier and/or from a PCell).

Other CRS parameters may be configured for extension carriers and/orcarrier segments. For example, the variable, v, and cell-specificfrequency shift, v_(shift), which may define a position in the frequencydomain for the different CRSs, may be determined differently for anextension carrier. For example, v_(shift) may be set to zero forextension carriers. Accordingly, for an extension carrier and/or carriersegment, the CRS mapping pattern and/or position in the frequency domainmay be different (e.g., relative to LTE R10).

The density of the CRS in the frequency domain (e.g. the number of REsto which CRS may be mapped within a RB) may be configured for anextension carrier. For example, one RE per RB per OFDM symbol may beused for CRS transmission on an extension carrier.

CRS transmission and/or a set of CRS related parameters may beconfigured per extension carrier and/or carrier segment, or per a groupof extension carriers and/or carrier segments). CRS transmission onextension carriers and/or carrier segments may be configured dependingon the CP type (e.g., normal CP or extended CP) used for the extensioncarrier and/or carrier segment. Configuration related signaling may beprovided from a serving cell linked to the extension carrier, /or from aPCell, and/or from another serving Cell.

CRS, if configured, may be transmitted on extension carriers and/orcarrier segments in an MBSFN subframe (e.g., if PMCH may not be carriedon any extension carrier and/or carrier segment). In an MBSFN subframe,if PDSCH is transmitted in the carrier segments configured for a servingcell, the PDSCH transmission may use substantially the same CRSconfiguration for carrier segments corresponding to a non-MBSFNsubframe. CRS may not be transmitted in OFDM symbols of carrier segmentscorresponding to the MBSFN region of the MBSFN subframe, or may not betransmitted in carrier segments in any MBSFN subframe. In an MBSFNsubframe, Extension CRS defined for extension CP may be used for carriersegments.

CRS transmission may be configured per extension carrier (e.g.,depending on a TM supported for the extension carrier). CRS transmissionmay be configured per carrier segments of a serving cell (e.g.,depending on a TM supported for the carrier segments). It should beappreciated that any combination of the herein described CRSconfigurations may be applied for CRS configuration of one or moreextension carriers and/or carrier segments.

A set of CRS structure and/or mapping configurations and/or patterns(e.g., as described herein) may be pre-defined, and may be configurable,for extension carriers and/or carrier segments. CRS structure and/ormapping configurations and/or patterns (e.g., a set of CRS structureand/or mapping configurations and/or patterns) may be used to configureone or more UEs. For example, a UE, in response to being configured withextension carriers and/or carrier segments, may be configured with oneor more (e.g., a set of) CRS structure and/or mapping configurationsand/or patterns (e.g., via RRC signaling and/or broadcast signaling). AUE previously configured with extension carriers and/or carrier segmentsand/or any CRS structure and/or mapping configurations and/or patternsmay be reconfigured with one or more (e.g., a set of) CRS structureand/or mapping configurations and/or patterns (e.g., via RRC signalingand/or broadcast signaling).

CSI-RS structure and/or design may be configured for extension carriersand/or carrier segments. For example CSI-RS may be used for assistingsynchronization operation for extension carriers and/or carrier segmentsat a UE.

Antenna ports may be redefined for CSI-RS. CSI-RS transmission may beconfigured per extension carrier and/or per UE (e.g., depending on a TMconfigured for the extension carrier. CSI-RS transmission may beconfigured per carrier segments of a serving cell and/or per UE (e.g.,depending on a TM configured for the carrier segments).

A set of CSI-RS structure and/or mapping configurations and/or patterns(e.g., as described herein) may be pre-defined, and may be configurable,for extension carriers and/or carrier segments. CSI-RS structure and/ormapping configurations and/or patterns (e.g., a set of CSI-RS structureand/or mapping configurations and/or patterns) may be used to configureone or more UEs. For example, a UE, in response to being configured withextension carriers and/or carrier segments, may be configured with oneor more (e.g., a set of) CSI-RS structure and/or mapping configurationsand/or patterns (e.g., via L1 signaling or L2/3 signaling). A UEpreviously configured with extension carriers and/or carrier segmentsand/or any CRS structure and/or mapping configurations and/or patternsmay be reconfigured with one or more (e.g., a set of) CSI-RS structureand/or mapping configurations and/or patterns (e.g., via L1 signaling orL2/3 signaling).

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element may be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, WTRU, terminal, base station, RNC, or any host computer.Features and/or elements described herein in accordance with one or moreexample embodiments may be used in combination with features and/orelements described herein in accordance with one or more other exampleembodiments. For example, a UE may be configured in accordance withextension DM-RS structure and/or mapping, CRS for extension carriersand/or carrier segments, and/or CSI-RS for extension carriers and/orcarrier segments, in any combination.

What is claimed:
 1. A method comprising: transmitting a first timeslotof a subcarrier, the first timeslot having a first plurality of resourceelements that are ordered from a first resource element to a lastresource element, wherein transmitting the first timeslot comprises:transmitting a first symbol in a select one of the first plurality ofresource elements that is not the last resource element, wherein thefirst symbol is a user equipment-specific demodulation reference signal;and transmitting a second symbol in the last resource element of thefirst plurality of resource elements, wherein the second symbol is otherthan a user equipment-specific demodulation reference signal.
 2. Themethod of claim 1, further comprising transmitting a third symbol in asecond select one of the first plurality of resource elements that isnot the last resource element, wherein the third symbol is a userequipment-specific demodulation reference signal.
 3. The method of claim2, wherein the first and second select ones of the first plurality ofresource elements, respectively, are adjacent to one another in thefirst timeslot.
 4. The method of claim 2, wherein the first and secondselect ones of the first plurality of resource elements, respectively,are spaced apart from one another in the first timeslot.
 5. The methodof claim 1, further comprising transmitting a second timeslot of thesubcarrier, the second timeslot having a second plurality of resourceelements, wherein transmitting the second timeslot comprisestransmitting a third symbol in a select one of the second plurality ofresource elements, wherein the third symbol is a user equipment-specificdemodulation reference signal.
 6. The method of claim 5, wherein thefirst symbol and the third symbol are located in substantiallyequivalent positions relative to the first and second pluralities ofresource elements, respectively.
 7. The method of claim 5, wherein thefirst symbol and the third symbol are located in different positionsrelative to the first and second pluralities of resource elements,respectively.
 8. The method of claim 1, further comprising: transmittinga first timeslot of a second subcarrier, the first timeslot of thesecond subcarrier having a second plurality of resource elements thatare ordered from a first resource element to a last resource element,wherein transmitting the first timeslot of the second subcarriercomprises: transmitting a third symbol in a select one of the secondplurality of resource elements that is not the last resource element,wherein the third symbol is a user equipment-specific demodulationreference signal; and transmitting a fourth symbol in the last resourceelement of the second plurality of resource elements, wherein the fourthsymbol is other than a user equipment-specific demodulation referencesignal.
 9. The method of claim 8, wherein the first symbol and the thirdsymbol are located in different positions relative to the first andsecond pluralities of resource elements, respectively.
 10. The method ofclaim 8, wherein the first subcarrier is staggered from the secondsubcarrier.
 11. A wireless transmit/receive unit (WTRU) comprising: aprocessor that causes the WTRU to transmit a first timeslot of asubcarrier, the first timeslot having a first plurality of resourceelements that are ordered from a first resource element to a lastresource element, wherein the WTRU transmits the first timeslot by:transmitting a first symbol in a select one of the first plurality ofresource elements that is not the last resource element, wherein thefirst symbol is a user equipment-specific demodulation reference signal;and transmitting a second symbol in the last resource element of thefirst plurality of resource elements, wherein the second symbol is otherthan a user equipment-specific demodulation reference signal.
 12. TheWTRU of claim 11, wherein the WTRU further transmits the first timeslotby transmitting a third symbol in a second select one of the firstplurality of resource elements that is not the last resource element,wherein the third symbol is a user equipment-specific demodulationreference signal.
 13. The WTRU of claim 12, wherein the first and secondselect ones of the first plurality of resource elements, respectively,are adjacent to one another in the first timeslot.
 14. The WTRU of claim12, wherein the first and second select ones of the first plurality ofresource elements, respectively, are spaced apart from one another inthe first timeslot.
 15. The WTRU of claim 11, wherein the processorfurther causes the WTRU to transmit a second timeslot of the subcarrier,the second timeslot having a second plurality of resource elements,wherein transmitting the second timeslot comprises transmitting a thirdsymbol in a select one of the second plurality of resource elements,wherein the third symbol is a user equipment-specific demodulationreference signal.
 16. The WTRU of claim 15, wherein the first symbol andthe third symbol are located in substantially equivalent positionsrelative to the first and second pluralities of resource elements,respectively.
 17. The WTRU of claim 15, wherein the first symbol and thethird symbol are located in different positions relative to the firstand second pluralities of resource elements, respectively.
 18. The WTRUof claim 11, wherein the processor further causes the WTRU to transmit afirst timeslot of a second subcarrier, the first timeslot of the secondsubcarrier having a second plurality of resource elements that areordered from a first resource element to a last resource element,wherein the WTRU transmits the first timeslot of the second subcarrierby: transmitting a third symbol in a select one of the second pluralityof resource elements that is not the last resource element, wherein thethird symbol is a user equipment-specific demodulation reference signal;and transmitting a fourth symbol in the last resource element of thesecond plurality of resource elements, wherein the fourth symbol isother than a user equipment-specific demodulation reference signal. 19.The WTRU of claim 18, wherein the first symbol and the third symbol arelocated in different positions relative to the first and secondpluralities of resource elements, respectively.
 20. The WTRU of claim18, wherein the first subcarrier is staggered from the secondsubcarrier.
 21. A wireless transmit/receive unit (WTRU) comprising: aprocessor that causes the WTRU to transmit a reference signal in selectsubframes of a radio frame in an extension carrier, wherein the selectsubframes are determined in accordance with an indication ofperiodicity.
 22. The WTRU of claim 21, wherein the indication ofperiodicity comprises a parameter of a configuration received by theWTRU.